It is desirable that the operation of a knitting machine be immediately stopped when a malfunction occurs to prevent the production of waste knit fabric and/or to prevent damage to the parts of the knitting machine. The first types of stop motions employed on knitting machines were entirely mechanical. For example, U.S. Pat. No. 1,727,171 discloses one such entirely mechanical stop motion device in which a pivoted detector lever is positioned to be engaged by a needle with a broken butt traveling along a higher than normal path of travel. The detector lever is mechanically connected to the stop motion mechanism so that the operation of the knitting machine is stopped when the detector lever is engaged by a needle with a broken butt. It is extremely difficult to maintain this type of mechanical linkage in proper adjustment and to immediately stop the knitting machine when a malfunction occurs.
More recently it has been the practice to utilize electro-mechanical activator devices to stop the knitting machine upon the occurrence of various types of malfunctions, such as improperly positioned latches on the knitting needles, broken yarns, broken needle butts and the like. These electro-mechanical activator devices usually include an electrical detector switch which is positioned to be operated when a malfunction occurs. The detector switch operates an electrically operated solenoid connected to the knitting machine stop motion. These known types of solenoids are either of the type which remain energized until a malfunction occurs, or of the type which are energized when a malfunction occurs and remain energized until the malfunction is corrected. In either case, the solenoid uses unnecessary amounts of electrical energy and the useful life of the solenoid can be reduced by the extended time in which electrical energy is supplied thereto.